Methods, apparatus and media for magnetically recording information

ABSTRACT

Methods, apparatus and media for magnetically recording at least first and second color components of an image employ anisotropic magnetizable particles in a matrix. The first color component is recorded by selectively orienting and disorienting first groups of anisotropic particles, and the second color component is recorded by selectively orienting and disorienting second groups of anisotropic particles.

United States Patent [191 Jeffers July 9, 1974 [54] METHODS, APPARATUS AND MEDIA FOR 3,555,556 l/l971 Nacci 346/74 MT MAGNETIC ALLY RECORDING 3,562,760 2/1971 Cushner et al 346/74 MT INFORNIATION R25,822 7/1965 Tate 346/74 MP [75] Inventor: Frederick J.Jeffers, Altadena, Calif. P imary Examihe James W MO-ffiu r r Asslgneel fil & Howell p y chlcago, Attorney, Agent, or FirmBenoit Law Corporation 22 Filed: Mar. 10, 1972 [57] ABSTRACT 21 Appl. No.: 233,646

, Methods, apparatus and media for magnetically recording at least first and second color components of g 85 an image employ anisotropic magnetizable particles in 58] H d 46/74 M 74 MT a matrix. The first color component is recorded by se- 8 0 are /5 4 lectively orienting and disorienting first groups of anisotropic particles, and the second color component is recorded by selectively orienting and disorienting sec- 5 g gi gif end groups of anisotropic particles. 3,320,523 5/1967 Trimble 3 46/74 M 58 Claims, 20 Drawing Figures 56 LI G H T j l l. 57 63 lllllzlglllllllllllllllllllll RED IO e-oio e o'o e o o e'o o 24 c RGBRGBRGBRGB ,so GREEN DEGAUSS i l e e oee-o e-o-o-e-o-ol 24 RGBRGBRGBRGB PATENTEDJUL 91974 SHEHSUF'I FRQNIIG. 7b

MAGrM FIG. 7c

. TONE YELLOW x87 TRANSFER FIX DEGAUSS PATENTEDJUL 91974 DEGAUSS DeAuss c M Y c M Y c M Y c M Slim 6 0F 7 LIGHT e d'd G Id did LIGHT LIGHT DEGAUSS METHODS, APPARATUS AND MEDIA FOR MAGNETICALLY RECORDING'INFORMATION U.S. Pat. application Ser.'No. 233,664, filed Mar. 10, 1972, by Sherman W. Duck, and assigned to the subject assignee.

' BACKGROUND OF THE INVENTION 1. Field of the invention The-subject invention relates to methods, apparatus and media for magnetically recording information and, more particularly, to methods, apparatus and media in which information is magnetically recorded by processes including a magnetic orientation of ferromagneticparticles; I

2. Description of the Prior Art Magnetic imaging has been the subject of serious invest-igation in.recent years, since it has several advantages over more conventional imaging techniques.

For instance, magnetic imaging offers the prospect of an avoidance of time-consuming and delicate chemical processing steps now required in customary photography Magnetic imaging also offers the prospect of an avoidance of expensive and potentially dangerous high voltage equipment now required in electrostatic xerographyand related techniques.

' Theres'till exists a need, however, for improvements in'magnetic imaging means and methods in general, and for advanced magnetic color imaging techniques and equipment.

SUMMA'R'Y oF THE I VENTION From one aspect thereof, the subject invention resides in a methodof recording at least first and second colorcomponents of an image. This aspect of the invention more specifically resides in the improvement comprising in combination the steps of providing color component deriving devices for deriving said color components, providing first and second groups of sphericaL-magne'tizable, uniaxially anisotropic particles in a matrix, providing said first and second color components with the aid of said color component deriving devices and said image, selectively orienting and disorienting particles in the first groups to provide a record of the provided first color component, and selectively orienting and disorienting particles in the second group to provide a record of the provided second color component.

A preferred embodiment of the invention just defined includes the further steps of providing magnetic printout agents, magnetically printing out the record of the first color component with one of said magnetic printout agents, and magnetically printing out the record of the second color component with another of said magneticprintout agents so as to provide a copy of the image.

From another aspect thereof, the subject invention resides in a method of recording at least first and second color components of an image. This aspect of the invention more specifically resides in the improvement comprising in combination the steps of providing color component deriving devices for deriving said color components, providing first and second groups of anisotropic particles in a matrix, orienting particles in the 2 first. groups substantially in parallel to a firstaxis, providing said first and second color components with the aid of said color componentderiving devices and said image, orienting particles in the second groups substantially in parallel to a second axis different from the first axis, changing the orientation of particles in selected groups of the first groups to provide a record of the provided first color component, and changing the orientation of particlesin selected groups of the provided second groups to provide-a record of the second color component.

While spherical, magnetizable, uniaxially anisotropic particles are presently preferred in the practice of the subject invention, it should be noted that the invention is not intended to be limited to the use of such particles, except where such a limitation is expressly stated in the course of the subject disclosure and the appendent claims.

From another aspect thereof, the subject invention resides in a method of recording at least first and second color components of an image. This aspect of the invention more specifically resides in the improvement comprising in combination the steps of providing color component deriving devices for deriving said color components, providing first'and second groups of anisotropic magnetizable particles in a matrix, providing said first and second color components with the aid of said color component derivingdevices and said image, orienting particles in selected groups of the first groups substantially in parallel to a first axis to provide a record of the provided first color component, and orienting particlesv in selected groups of the second group substantially in parallel to a second axis different from the first axis to provide a record of the provided second color component.

The subject invention also provides novel color printout techniques. Thus, the subject invention further resides in a method of printing out a record of at least two color components of an image, in which a first color component is recorded in selectively oriented and disoriented first groups of anisotropic particles, and a s econd color component is recorded in selectively oriented and disoriented second groups of anisotropic particles;

The latter aspect of the invention comprises the combination of steps of magnetizing only the oriented first groups of particles, printing out the magnetization of these magnetized first groups with the aid of a first magnetic color toner, magnetizing only the oriented second groups of particles, and printing out the magnetization of the magnetized second groups with the aid of a second magnetic color toner.

The invention further resides in a method of printing out with a magnetic printout agent, an information record represented by selectively magnetized and orientedanisotropic magnetizable particles and disoriented mangetizable particles. The latter method comprises in combination the steps of subjecting the oriented and the disoriented particles to magnetizing fields, and subjecting the oriented and the disoriented particles to demagnetizing fields having a maximum amplitude below a single-particle coercivity of the oriented and the disoriented particles and above one-half that single-particle coercivity.

While the latter aspect of the subjectinvention is particularly beneficial in the printout of color .records, it

stance, be employed in black-and-white printing process'es. Y

The subject invention also resides in novel recording apparatus. i 3 I Accordingly, the invention resides in apparatus for recording at least first and second color components of an image. More specifically, the invention resides in the improvement comprising, in combination, first and second color component deriving devices for deriving said first and second color components, respectively, a recording medium having a matrix, and first and second groups of spherical, magnetizable, uniaxially anisotropic particles located in the matrix, means operatively associated with said first color component deriving devices and the recording medium for providing a record of the first color component by selectively orienting and disorienting particles in the first groups, and means operatively associated with said second color component deriving devices and the recording medium for providing a record of the second color component by selectively orienting and disorienting particles in the second groups.

Froma similar aspect thereof, the invention resides in apparatus for recording at least first and second color components of an image, comprising the combination of first and secondcolor component deriving devices for deriving said first and second color components, respectively, a recording medium having a matrix, and first and second groups of anisotropic magnetizable particles located in the matrix, means operatively associated with the recording medium for orienting particles in the first groups substantially in parallel to a first axis, means operatively associated with the recording medium for orienting particles in the second groups substantially in parallel to a second axis different from the first axis, means operatively associated with said first color component deriving devices and the recording medium for providing a record of the first color component by changing the orientation of particles inselected groups of the first groups, and means operatively associated with said second color component deriving devices and the recording medium for providing a record of the second color component by changing the orientation of particles in selected groups of thesecond groups.

The invention resides further in apparatus for recording at least first and second color components of an image, comprising the combination of first and second color component-deriving devices for deriving said first and second color components, respectively, a recording medium having a matrix, and first and second groups of anisotropic magnetizable particles located in the matrix, means operatively associated with said first color component deriving devices and the recording medium for providing a record of the first color component by orienting particles in selected groups of the groups substantially in parallel to a first axis, and means operatively associated with said second color component deriving devices and the recording medium for providing a record of these second color components by orienting particles in selected groups of the second groups in parallel to a second axis different from the The invention moreover resides in apparatus for printing out a record of at least two color components of an image with the aid of first and second magnetic color toners, in which record selectively oriented and disoriented first groups of anisotropic magnetizable particles represent a first color component and selectively oriented and disoriented second groups of anisotropic magnetizable particles represent a second color component.

The latter apparatus comprises the combination of means operatively associated with the record for magnetizing only the oriented first groups of particles, means operatively associated with the record for printing out a record of the magnetization of the magnetized first groups, with said first color toner means operatively associated with the record for magnetizing only the oriented second groups of particles, and means operatively associated with the record for printing out a record of the magnetization of the magnetized second groups with said second color toner.

The invention furthermore resides in apparatus for improving the magnetic contrast of an information record represented by selectively magnetized and oriented anisotropic particles, and relatively disoriented magnetized particles, comprising, in combination, means operatively associated with the record for subjecting the oriented and the disoriented particles to variable magnetic demagnetizing fields, and means connected to the operatively associated means for adjusting the maximum amplitude of the magnetic demagnetizing fields to a value below a single-particle coercivity. of the oriented and the disoriented particles and above one-half of this single-particle coercivity whereby the disoriented particles are demagnetized and said oriented particles remain magnetized.

The subject invention also provides a number of novel recording media for recording at least two color componentsof a luminous image.

These recording media typically comprise means including a plurality of interspersed first filter elements for passing luminous impressions corresponding to one of the color components and second filter elements for passing luminous impressions corresponding to the other of these color components as well as a matrix, anisotropic magnetizable particles dispersed in this matrix, and means operatively associated with the interspersed first and second filter elements and with the matrix for selectively rotating anisotropic particles in the matrix in response to transmitted luminous impressions.

The subject invention also provides information records which have utility of their own since they may be stored, distributed or sold for subsequent magnetization and printout, as desired. Accordingly, the subject invention resides in a record of at least first and second color components of an image derived by first and second color component deriving devices, respectively, comprising in combination a matrix, first groups of selectively oriented and relatively disoriented anisotropic magnetizable particles located in the matrix and representing the first color component derived by said first color component deriving devices, and second groups of selectively oriented and relatively disoriented anisotropic magnetizable particles located in the matrix and representing the second color component derived by said second color component deriving devices.

BRIEF DESCRIPTION OF THE DRAWINGS The subject invention and various aspects thereof willbecome more readily apparent from the following detailed description of preferred embodiments of the invention, illustrated by way of example in the accompanying drawings, in which:

FIG. 1 is a diagrammatic longitudinal section through a recording medium according to a preferred embodiment of the subject invention;

FIG. 2 is a diagrammatic illustration of particle orientations occurring in the practice of various embodiments of the subject invention;

FIG. 3 is a circuit diagram of energizing and magnetizing apparatus useful in the practice of various embodiments of the subject invention;

FIG. 4 is an I-H graph useful to the understanding of the operation of the apparatus of FIG. 3;

FIG. 5 is a flow-sheet illustrating methods and apparatus for preparing the recording medium of FIG. I for a recording operation;

FIGS. 6a through 6c constitute a flow sheet depicting a process and equipment for preparing a color image record in accordance with a preferred embodiment of the subject invention;

FIGS. 7a through 7d constitute a flow sheetdepicting color printout methods and apparatus in accordance with a further preferred embodiment of the subject invention;

FIG. 8 is a perspective view of a part of a recording medium in accordance with another preferred embodiment of the subject invention;

FIGS. 9a through 90 constitute a flow sheet depicting color recording techniques and apparatus in accordance with yet another preferred embodiment of the subject invention; and

FIGS. l0athrough 10a constitute a flow sheet depicting color printout techniques and equipment in accordance with yet a further preferred embodiment of the subject invention.

In the accompanying drawings, like reference numerals among different figures designate like or functionally equivalent parts.

DESCRIPTION OF PREFERRED EMBODIMENTS The magnetic recording medium l0 according to a preferred embodiment of the subject invention shown in FIG. 1 includes a transparent substrate 12 which may be a sheet of glass or an organic equivalent thereof, such as a transparent high-temperature polyimide or polybenzamidazole.

The substratelZ carries on one side thereof an array 13 of recurring tricolor filter elements designated by R,

G, and B, respectively, for the primary colors red, green and blue. An interdigitated electrode structure 15 including interdigitated first and second electrodes 16 and 17 is located on the transparent substrate l2. The deposition of electrode structures on a transparent substrate is a well-established art and does not as such form part of the subject invention. Suffice to say therefore, that the electrode structure 15 may be deposited on the substrate 12 by evaporation, painting or sputtering, and that preferred electrode materials include gold, indium, chromium and aluminum. The eventhe photoconductive layer 22 is not generally critical, but a layer thickness of about 3 to 10 microns is presently preferred.

For further information, where needed or desired, on the structure and operation of a photoconductive as sembly of the type herein employed, reference should be had to the copending US. Pat. application Ser. No. 29,584, Magnetic Imaging, filed Apr- 17, I970, and now US. Pat. No. 3,717,460 by Sherman W. Duck, Frederick J. Jeffers and James U. Lemke, assignors of the subject assignee, and the copending US. Pat. application Ser. No. 29,583, Magnetic Imaging, filed Apr. 17, I970, and now US Pat. No. 3,717,459 by Richard J. McClure, assignor of the subject assignee.

The recording medium 10 further includes a matrix 24 deposited on the photoconductive layer 22. Magne tizable particles 25 are dispersed in large numbers through the matrix layer 24.

The magnetizable particles 25 are anisotropic so as to have an easy axis of magnetization. If desired, the anisotropy of the particles 25 may be a shape anisotropy, provided by acicular particles. In accordance with a preferred embodiment, however, the particles 25 are spherical and uniaxially anisotropic, as well as magnetizable.

Uniaxial anisotropy" as herein employed refers to the type of magnetocrystalline' anisotropy of a magnetizable material that is characterized by a single axis of easy magnetization or minimum internal magnetic energy, and by external magnetization minima or internal magnetic energy maxima in a plane intersecting the easy axis substantially at right angles. Uniaxial anisotropy is a well-known magnetic property and as such does not. require particular elaboration. Needless to say, the uniaxial anisotropy of the particles herein employed should, of course, be high enough for an orientation effect of the type herein employed, and the particles should be magnetizable and capable of retaining an imposed magnetization.

Preferred uniaxially anisotropic materials for the particles 15 include hexagonal cobalt, manganese bismuthide (MnBi), or a cobalt compound of the type Co R, wherein R is a rare-earth metal, such as gadolinium or yttrium which arefrequently classified as rare-earth metals. Many other hard magnetic materials are, however, suitable for the practice of the subject invention.

The expression magnetizable" as herein employed with respect to the ferromagnetic particles refers to the well-known property of hard ferromagnetic particles of retaining an imposed magnetization after removal of the magnetic field with which the magnetization has been imposed. The expression magnetizable" as herein employed is intended to be broad enough to cover not only particles which are to be or can be magnetized in the latter sense, but also particles which have been magnetized in the latter sense.

In accordance with another preferred embodiment of the subject invention, the particles 25 are of singledomain size. As is well known in magnetics, the expres sion single-domain refers to the absence of Bloch walls in the particles. Due to this absence, the .uniaxially anisotropic single-domain particles are rotated I physically by the'aligning magnetic field, rather than undergoing merely realignment of magnetic spins within the particle.

' In accordance with a further preferred embodiment of the subject invention,-the particles are spherical in shape. This permits the-particles to rotate with the least resistance as compared to acicular shapes. It also has the substantial advantage that the velocity of undesirableparticle agglomeration is very substantially reduced because of the poor hydrodynamic properties of spherical configurations. In thisrespect, the center-tocenter particle separation in the layer 24 preferably is in excess of about two particle diameters to curbundesirable particleagglomeration during the rotation of the particles in the fluidized matrix. Experiments have indicated that particle loading densities of as low as four percent by volume afford adequate toning properties fora printout of the magnetic record with the aid of magnetic toner. This loading density provides a center-to-center particle separation of about three particle diameters. v

The expression spherical as herein employed with respect to the ferromagnetic particles is intended to be braod enough to cover not'only perfect spheres but also those spheroids and hydrodynamically equivalent shapes which provide'the ferromagnetic particles with rotatability and other hydrodynamic properties in the matrix. which are equivalent in practice to hydrodynamic properties of particles of exact spherical shape.

informationmodulated influence, will revert to the first state in which the ferromagnetic particles are again substantially stationary.

By way of example and not by way of limitation, suitable materials for the matrix 16 include acetals, acryl- 'ics, polyeste rs, silicones, and vinyl resinshaving a subs tantially infinite room temperature viscosity and a substantially fluid viscosity temperature of the order of about 100C to 150C. Other suitable materials for the matrix 16 include waxes which typically exhibit a relatively sharp melting point transition. If desired, wax and polymer mixtures may be employed.

in the matrix 24. The power source 30 is dimensioned and the variable resistor 31 is adjusted so that the thermal image has sufficient energy for effecting a desired change in the matrix 24. Principles of preferred exposure techniques, such as exposures within a narrow exposure band that progresses in a direction parallel to the electrodes 16 and 17, may be derived from the above mentioned copending Duck, Jeffers and Lemke application and copending McClure application.

The thermal image produced in the matrix 24 upon exposure of the medium 10 selectively transforms portions of the matrix to the second state in which particles 25 are rotationally mobile. This enables an information-responsive orientation or deliberate disorientation of particles 25 in the matrix 24.

To facilitate an understanding of the subject disclosure, preferred orientation of the uniaxially anisotropic particles 25 in the matrix 24 are symbolically illustrated in FIG. 2. These symbols concern the orientation of the magnetocrystalline easy axis of magnetization or minimum internal energy axis of the uniaxially anisotropic ferromagnetic particles 25. As may be seen from FIG. 2, an x-orientation" is present if the particles are oriented parallel to an x-axis, which extends horizontally in the plane of the paper on which FIG. 2 is drawn. The particles have a y-orientation when they are oriented parallel to a y-axis, which extends perpendicularly through the plane of the paper. A z-orientation" is present if the particles are oriented parallel to a zaxis,'which extends vertically in the plane of the drawing paper.

FIG. 2 also diagrammatically depicts a low energy state of particles 25 which occurs when particles are magnetized and a matrix portion is fluidized so that particles are permitted to rotate and seek a low-energy state in which their net magnetic moment is minimized. In this manner the particle orientations are randomized". While it may be true that the latter term may not strictly be applicable in its classical sense, it will be noted that theparticles presently under consideration are-disoriented relative to the x, y and z-orientations, wherefore the symbol at is employed for the depicted low-energy state.

The illustrated preferred embodiment requires for its operation magnetizing equipment 34 that will selectively provide a vectorial magnetic field for orientation purposes, magnetizing fields for magnetizing purposes The free surface of the matrix 24 may be covered by a thin layer 27 which precludes undesirable deformations of the matrix 24 and which protects the matrix from damage during printout or other handling. The layer 27 may be. a thin foil of a plastic material, such as Teflon (poly'tetrafluorethylene) or Mylar or Cronar'. (Registered Trademark of E. I. du Pont de Neumours &Company).

The current supply bar 18 is connected to an electric power sourcev through a variable resistor 31, while the current supply bar- 19 is connected to the source 30 through a normally open switch 32. The recording medium 10 is activated by closing the switch 32. Electric currents will flow between adjacent electrodes 16 and.

I7 where portions of the photoconductive layer are hit by incident light. In this manner, a thermal image that corresponds to the luminous input image is produced and anhysteretically declining fields for demagnetizing purposes.

According to FIG. 3, the magnetizing equipment 34 is composed of a magnetizer 35 and an energizer 37. The magnetizer includes an electrically energizable magnet coil or bobbin 38. The coil 38 is symbolic for the many types of electromagnetic magnetizing structures that may be employed. These structures may, for instance, take the form of a solenoid or Helmholz coil that encompasses or contains the recording medium 10 (see the types of magnetizing coils disclosed in U.S. Pat. No. 2,793, l 35, by J. C. Sims et al., issued May 21,

1957, the disclosure of which is herewith incorporated by reference herein). lf desired, conventional types of ferromangetic magnetizing structures which have pole pieces that have all or part of the recording medium 10 located thereat or therebetween may be employed in the magnetizer 35. Because of the geometrical dimensions of the recording medium 10, it may be found prefmagnetic field with which erable in practice to use a differently shaped magnetiz- '35 with energizingcui'rent. The energizer 37 includes two series-connected electric current sources 39 and 40. The source 39 may be of a conventional directcurrent type. The junction between the sources 39 and 40 is connected through a lead 41 to a terminal 42 of the coil 38. The other terminal 43 is connected-to the source 39 by way of a potentiometer 44 and a normally open switch 45. The intensity of the magnetic field provided by the magnetizer 35 is variable by adjustment of the potentiometer 44.

The terminal 43 of the magnetizer 35 is also connected to the source 40 by way of a normally closed switch 50,.a capacitor 45, a potentiometer 46 and a normally open switch 47. The source 40 is a source of alternating current of relatively high frequency. When the switch 47 is closed, the source 40 is connected to the magnetizer 35 which then produces an alternating the particles 25 may be degaussed. 'On the other hand, when the switch 45 is closed while the switch 47 is open, the source 39 is connected to the bobbin 38 and the magnetizer 35 provides a continuous magnetic orienting field. Magnetic particles 25 are oriented in the desired direction (x, y, or 2) when they are exposed to the latter orienting field while the particular matrix portions are fluidized. The position of the recording medium relative to the magnetizer 35 determines the direction (e.g., x, y or z) in which the particles are oriented.

In all degaussing or demagnetizing operations, the source 40 may have an anhysteretically declining output. In practice, however, the amplitude of the alternating current provided by the source 40 may be constant, and the particles 25 and the magnetizer 35 may be moved relative to each other to provide the requisite anhysteretic magnetic field amplitude decrease for degaussing or magnetic erasure; The degaussing or demagnetizing operations herein referred to are not nece'ssarily directed to the demagnetization or degaussing of particles individually. Of course, in thecase of multidomain particles, degaussing or demagnetization of the particles individually is possible. However, in the case of single-domain particles, the particles are not demagnetized or degaussed individually. Rather, magnetic moments of adjacent particles are flipped into opposition to each other to provide no or only a neglible net magnetic moment.

It will be found in the practice of the subject invention that randomly oriented or disoriented particles 25 are sometimes undesirably magnetized when only adjacent oriented particles are desired to be magnetic.

Asindicated in FIG. 4, if the remanent magnetization of oriented particles is designated by 1,, then the remanent magnetization of randomly oriented or disoriented particles is substantially equal to I,,/2. This, in practice provides a considerable background noise that is prone to impair the quality of the magnetic information record and of magnetic printout operation. This background noise is substantially eliminated by applying to the particles 25 in the recording medium an anhysteretic magnetic field of declining'amplitude which has a maximum amplitude A of a value below H and above Flt/2. In this connection, the symbol H stands for the single-particle coercivity of the particles 25.

. 0 i If it is considered that the somewhat idealized curve 48 in FIG. 4 indicates the course of the remanent magnetization of oriented particles in response to the application of an opposing magnetic field that reaches a magnitude greater than H while the curve 49 shows the course of the remanent magnetization of randomly .oriented or disoriented particles 25, then it will be realized that regions'containing oriented particles 25 will not be demagnetized, but that regions containing randomly oriented or disoriented particles will be degaussed or demagnetized by the application of the anhysteretic demagnetizing field having a maximum amplitude of A. I

I would like to mention at this point that FIG. 4, as well as my idea of exploiting its principles in the manner herein set-forth originated with Dr. Chikazumis book PHYSICS OF MAGNETISM (Wiley & Sons, 1964) p. 292.

According to FIG. 3, a resistor 51 is connected in parallel to the normally closed witch 50. As long as the switch 50 remains closed, the resistor 51 is shunted and sufficient current is supplied from the source to the coil 38 to provide magnetic degaussing fields that have a maximum amplitude above H The resistor 51 is so dimensioned that the current supplied to the coil 38 drops upon opening of the switch50 to such a value that the maximum amplitude of the degaussing current is located at the value A between H, and Pi /2 The degaussing operation of randomly oriented-or disoriented particles 25 proceeds practically in the same manner'as the degaussing operation of oriented particles, except that the degaussing field, because of its low maximum amplitude A, is not capable of degaussing oriented particles. If desired, the resistor 51 and the switch 50 may be connected in series with the potentiometer 46.

It should be understood at this juncture that the principles just disclosed are not limited in their application to a reduction of background noise in color records, but are of high utilityin the improvement of black-andwhite magnetic records in which randomly oriented or disoriented ferromagnetic particles are located adja cent to oriented ferromagnetic particles.

' To simplify matters, the x-orientation of the particles 25 has been indicated in FIG. 2 as extending parallel to the free outer surface of the matrix 24, whereby the yorientation will also extend parallel and the zorientation will extend perpendicularly to such outer matrix surface. This, indeed, is a viable system of orien tation that may be employed in practice and that has the advantage of a simplified magnetizing strucuture design.

In accordance with a preferred embodiment of the subject invention, however, the orthogonal x, y and z axes of orientation of the particles 25 are arranged so that these axes subtend like angles 53 relative to the outer surface 54 of the matrix 24. The resulting arrangement is perspectively illustrated in FIG. 8 with the aid of three anisotropic particles 25. As shown in that figure, the x, y and z axes extend through the corners ferred orientations for the particles 25. In practice, the

tration of these further embodiments, the showing of the recording medium 10 has been considerably simplified in FIGS. et seq. Briefly, the recording medium and matrix 24 have been shown as an elongate rectangle which is subdivided into red, green and blue regions, labeled R, G and B, respectively. These regions need not in practice be mutually segregated, but exist by virtue of the presence of the color filter elements 13 shown in FIG. 1. In consequence, a red region of the matrix 24 is a region to which only red light is admitted through the corresponding red filter element shown in FIG. 1. The same applies mutatis mutandis to the green and blue matrix regions.

Moreover, for the purpose of simplification, only one magnetic particle 25 is shown in FIGS. 5 et seq. within any color region. Again, it is to be understood that a large multitude of such particles are present in each of these color regions. While these simplifications are beneficial to an accelerated understanding of the disclosure, it should always be kept in mind that the recording medium '10 may in all figures be of the type disclosed in connection'with FIG. 1

The flow sheet of FIG. 5 illustrates methods and equipment for preparing the recording medium 10 for color recording purposes.

According to FIG. 5, the recording medium 10 is successively exposed to red, green and blue light. For this purpose, a source 56 of preferably white light 57 is provided. The source 56 may be an electrically energized lamp, such as, for instance, a low-voltage, hightemperature-incandescent lamp thatemits light which is'as white aspossible.

A red filter 58 is employed in conjunction with the light source 56 if an exposure of the recording medium 10 to red light is desired. Similarly, a green filter is used for a green-lightexposure,'and a blue filter is utilized for a blue-light exposure. Since this procedure is standard as such, the green-light exposure has been merely illustrated by a block 60, while a block 61 indicates a blue light exposure. If desired, the requisite red, green and blue filters may be part of a continually rotating color wheel.

The process of FIG. 5 preferably commences with a recording medium 10 in which the particles 25 are initially randomized. This initial randomization may bev As shown at the top of FIG. 5, red light extracted from the white light 57 by the filter 58 reaches, of course, the top of all elemental filters of the color filter structure (see 13 in FIG. 1). However, only the red filter elements will pass such red light to the corresponding elemental photoconductor portions. Accordingly, only the red matrix regions will become fluidized during the red-light exposure.

The magnetizer 34 subjects the recording medium 10 to a vectorial magnetic field M so that the particles 25 in the red matrix regions will rotate during the red-light exposure and will thus be oriented in parallel to the xaxis. This orientation having been effected, the redlight exposure is terminated so that the fluidized matrix portions can solidify, thereby freezing the x-orientation of the particles in the red matrix region.

As indicated by the block 63, the particles in the matrix 24 are thereupon degaussed, so as to avoid spot-tospot magnetic field interference during subsequent exposure. This degaussing operation may be effected with the equipment 34 of FIG. 3, with the switch 50 being closed so that the maximum amplitude of the degaussing field is above the above mentioned single-particle coercive force H To avoid background noise and other disturbances, it is preferable for the degaussing step of block 63 to be carried out in all three axial directions. The same applies to the further degaussing steps hereinafter to be described or referred to.

The recording medium 10 having been degaussed as indicated by the block 63, it is subjected to a greenlight exposure symbolized by the block 60. This exposure results in a fluidization of the green matrix portions in which particles 25 are'oriented in parallel to the y-axis by a vectorial magnetic field M provided by the magnetizer 34. After the green-light exposure has been terminated, the y-orientation of the latter particles becomes frozen and'the matrix 24 now contains particles that are oriented in the x-direction and particles that are oriented in the y-direction, in addition to randomly oriented particles. As indicated by the block 65, the r'ecordingmedium 10 is again degaussed in the manner previously described in connection with block 63.

The degaussed'recording medium 10 is thereupon subjected to a blue-light exposure during which the blue matrix regions are fluidized so that a vectorial magnetic field M provided by the magnetizer 34, is capable of orienting the particles in parallel to the zaxis. Tennination of the blue-light exposure and freezing of the imposed z-axis orientation is followed by an omnidirectional degaussing step 66 which may be of the same type as the degaussing steps 63 and 65.

- The result of the process of FIG. 5 is a recording medium which has distinctive red, green and blue regions by use of a recurrent tricolor filter system and which has magnetizable particles selectively oriented in three different directions as shown at the bottom of FIG. 5.

in the particular direction (here the x-direction) to provide a vectorial magnetizing field along the particular axis. Since the three axes of orientation extend orthogonally to each other, only one orientation of particles will be strongly magnetized at a particular time.

According to FIG. 6a, the color image to be recorded is-p'resent in the form of a color transparency 70 having red, yellow, cyan and white areas as indicated by the letters R, Y, C and W.

In FIG. 6a, the master record 70 is subjected to a redlight exposure provided by the white-light source 56 and red filter 58. The red light will penetrate the red, yellow and white regions of the master record 70 and will also penetrate the adjacent red elemental filters (see 13 in FIG. 1) of the recording medium 10. In contate. As indicated in connection with FIG. 2, this will A leadto a randomization or disorientation of the particular particles, since they have previously been magnetized as shown by the block 68. Accordingly, the letter d is shown in FIG. 60 within the red regions whose particles have become randomized or disoriented during the image-wise red exposure. No randomization takes place in any matrix region below the cyan master record area, since a cyan filter will not pass red light.

The recording medium is thereupon degaussed as indicated by the previously discussed block 63, and the particles in the green matrix portions are magnetized by vectorial magnetic feidls M as indicated by the block 72. t

As shown in FIG. 6b, the recording medium is thereupon subjected to a green-light exposure through the.

After the exposure step of FIG. 6b has been completed, the recording medium is first degaussed as indicated by the previously discussed block 63 and is then magnetized in the z-direction as indicated by the block As shown in FIG. 60, the recording medium 110 is thereupon subjected to a blue-light exposure through the master record 70. The oriented particles in blue matrix portionsbelow the cyan and white master record regions are disoriented since both of these regions are capable of passing blue light. No blue light is, on the other hand, passed by the red and yellow master record regions so that the particles in the corresponding blue matrix portions remain oriented. As indicated by the block 63 in FIG. 60, the completed informationrecord is once more degaussed in all three directions by degaussing fields having maximum amplitudes above the previously discussed single-particle coercivity H .The resulting information record is thus not of a type in which the information content resides in magnetic field gradients as such. Rather, the information. re-

corded in the medium 10 is contained in selective particle orientation and disorientation. The record shown at the bottom of FIG. 6c does have utility of its own,

whether it is in a magnetized or in a vdemagnetized state, since it can be stored, distributed or sold for a subsequent printout of the information.

An appropriate printout process according to a preferred embodiment of the subject invention is illustrated in FIGS. 7a through 7d.

According to the block 76 in FIG. 7a, the recording medium 10 is subjected to magnetization fields in parallel to the x-axis whereby oriented particles in the red matrix portions are magnetized. As indicated by the block 78, the recording medium 10 is thereupon subjected to degaussing fields having maximum amplitudes below the, single-particle coercivity I-I but above onehalf of such single particle coercivity. In terms of the apparatus of FIG. 3, these demagnetizing fields may be realized by opening the normally closed switch 50. The result, as previously mentioned, is a degaussing of all particles that are not oriented in the direction of previous magnetization (here x-direction).

The result. of the magnetization step 76 and partial degaussing step 78 is that the recording medium 10 in FIG. 7a presents a magnetic record of a first color component of the input image 70. Strictly speaking, this first component is a minus red or cyan component,

since the red-component image exposure of FIG. 6a

resulted in a disorientation of particles in portions where red light was able to reach a recording medium, while particles remained oriented, and thus axially magnetizable, in red matrix portions which remained unexposed during the red-component exposure step.

The magnetic record at FIG. 7a is toned with a magnetic toner that has a color which is complementary to the color to which the recording medium was exposed in FIG. 6a. In brief, this record is toned with a cyan toner as indicated by the box 80. Incidentally, it is not indispensable that the exact color sequence mentioned in FIGS. 7a through be used in a printout of the previously established color image record. However, while other techniques are operable, the illustrated technique is at least preferred for explanatory purposes since it follows a logical pattern relative to the exposure sequence at FIGS. 6a through 6c.

Magnetic toners are well known in the art of magnetic printing and-may include particles of iron, nickel, cobalt or ferromagnetic compositions. These ferromagnetic particles may be used as a magnetic toner for printout on a tacky surface. If printing out on a dry surface is desired, the ferromagnetic particles are preferably suspended in a toning liquid or provided with shells of fusible material. Suitable magnetic toners and toning and printout methods and equipment are, for instance, disclosed in U.S. Pat. No. 2,932,278, by .l. C. Sims, issued Apr. 12, 1960, US. Pat. No. 2,943,908, by J. P. Hanna, issued July 5, 1960, US. Pat. No. 3,052,564, by F. W. Kulesza, issued Sept. 4, 1962, and US. Pat. No. 3,250,636, by R. A. Wilferth, issued May 10, 1966.

These specifications and drawings of these patents are herewith incorporated by reference herein.

Direct printout of the magnetic record from the medium MI is facilitated by the presence of the toughcover coating 27 which protects the matrix 24 from damage during printout. If desired, printout may alternatively take place from an auxiliary medium, such as gammaferric oxide layer, unto which the magnetic record of FIG. 7a has been transferred by anhysteretic magnetic transfer field or the like. Suitable transfer techniques are disclosed in US. Pat. No. 2,738,383, by R. Herr et al., issued Mar. 13, 1956, the disclosure and drawing of which is herewith incorporated by reference herein.

Reverting to the embodiment specifically illustrated in FIG. 7a, a cyan toner image 81 forms itself at the location of themagnetized particles in the red matrix portion in which the particles 25 have not been disoriented. The toner image 81 is fixed against premature removal thereof during subsequent handling steps. A conventional fixative spray may be employed for fixing the toner image 81. If the applied toner, in a conventional manner, has fusible shells, then a flash of heat radiation may be employed for temporarily fixing the image 81. The fixing step is symbolically shown in the drawings by the block 83.

After the toner image 81 has been temporarily fixed, the recording medium 10 is subjected to the previously described degaussing step 63, magnetizing step 72 and special degaussing step 78 whereby all red matrix regions will bedemagnetized and all green matrix regions in which the particles 25 are still oriented in the ydirection will be magnetized to the exclusion of any other regions. The resulting magnetic record is thereupon toned with a magenta toner symbolized by the block 84.-The resulting magenta toner image 85 is temporarily fixed and the recording medium is subjected to the previously described degaussing step 63, magnetizing step 74 and special degaussing step 78.

In consequence, the z-oriented particles in unexposed blue matrix regions become magnetized. As indicated by the block 87, the resulting magnetic record is toned with yellow toner. The resulting yellow toner image 88v may also be temporarily fixed.

At this juncture it is well to recognize certain practical limitations in the illustration of the printout process.

' In reality, practically no color component of the input image- 70 will be recorded within only one triplet of red, green and blue matrix regions. Rather, a large number of these triplets will be available for each color detail. However, since no large plurality of triplet could be s hown'in the drawings, FIG. 7c may at the toner im ages 81 and 88 give the impression that a green toner image is created where there should be a yellow toner image adjacent to a cyan toner image. Of course, if one correctly substitutes the actually occurring multitude of triplets for the area of the yellow color component,

' and follows the same process with respect to the cyan color component, one will see that yellow and cyan toner images are, indeed, formed side by side without undue intermixture.

Keeping these limitations in the subject illustration of the actual process in mind, we can see that the toner images 85 and 88 combine to form a red toner image at the location of th red color component of the input image 70 shown in FIGS. 6a through 6c. The toner image 88 provides a yellow toner image at the location of the yellow color component of the input image 70. The toner image 81 provides a cyan toner image at the location of the cyan color component of the input image; Most significantly, no toner has been attracted to the recording medium portions that correspond in location to the white part of the input image 70. This lack of attraction is due to the disorientation of the particles 25 in thatrecording'medium region.

In consequence, white input image portions will be correctly represented aswhite areas upon printout of the toner images on a white paper. In a like manner,

light-transparent portions will remain light-transparent if the toner images are printed out on a transparent film. Black impressions on the input image will be printed out in black, since triplets adjacent black image regions will not be exposed so that the particles 25 located therein will remain aligned and thus magnetizable. In consequence, all three toners will be attracted to the particular regions so that their appearance will be dark or black.

The transfer of the toner images does not as such form part of the subject invention and is therefore illustrated by a block 90. Transfer techniques of the type disclosed in the above mentioned, incorporated toner patent may be employed. For instance, a transparent or white adhesive layer 91 may be provided on a sheet of white paper 92 so that the red, yellow and cyan toner images will cling to the paper and be removable therewith if the same is pressed against the recording medium 10 of FIG. 70.

The process of FIGS. 7a through d can be repeated many times for the production of a large number of prints of the recorded input image.

The recording medium 10 may be rendered reusable by a magnetization in all three directions followed by a uniform fluidization which will permit randomization of all the particles in the manner shown in FIG. 2 at d. However, the matrix 24 with included particles 25 should preferably-not be reused too often, since the particles 25 tend to agglomerate undesirably during recurring exposure steps. For reasons of economy, the matrix 24 and particles 25 assembly may be made removable from, and replaceable on the photoconductor 22 and electrode structure 15 assembly. In this connection, the layer 27 may serve as a substrate for the matrix 24.

Also, it will be noted that various substances are suitable for appropriately coloring the magnetic toners employed herein. By way of example, and not by way of limitation, magnetically attracted cyan, magenta, and yellow toner may be formed by coating magnetizable particles with solutions containing, respectively, phthalocyanine blue B for cyan, lithol maroon for magenta, and Hansa yellow T for yellow.

A further preferred embodiment of color recording method and equipment according to the subject invention is illustrated in FIGS. 9a through which, by way of example, address themselves to the problem of providing positive prints from a color negative record 100. While the recording process of FIGS. 6a through 60 operates on the principle of selective particle disorientation, the recording process of FIGS. 9a through 90 employs selective particle orientation. Accordingly, the latter process may start out with a recording medium that has its particles randomized or disoriented. In this manner, the medium preparation processes of FIG. 5 are rendered unnecessary.

The disoriented-particle recording medium 10 is subjected to a degaussing step 63 in which the particles are degaussed in all three directions of the orientation system. As shown in FIG. 9a, the color negative record 100, which may for instance be a photographic color negative, is exposed to cyan radiations provided by an association of a cyan filter 101 with the white light source 56.

The negative record has cyan, blue, red and black color regions designated, respectively, by the letters C, B, R and Bk. Those skilled in the art of color 100 represents a color negative of the previously described master record 70. The purpose of the process of FIGS. 9a through 9c is, accordingly, the provision of a record from which color print corresponding to the initial master record 70 can be printed out.

In contrast to the recording medium 10 so far described, the recording medium 10' employed in the process of FIGS. 9a through 90 includes a filter structure that is composed of cyan, magenta, and yellow filter elements. This filter structure has not particularly been shown in FIGS. 9a through 9c, since FIG. I makes an appropriate showing of a filter structure 13, with the difference that the red (R), green (G), and blue (B) filter elements are in FIGS. 9a through 90 replaced by corresponding cyan (C), magenta (M), and yellow (Y) filter elements.

The cyan radiations provided in FIG. 9a penetrate the cyan and blue master record areas and the cyan filter elements in the corresponding triplets of the recording medium 10. As a result, the cyan matrix portions below the cyan and blue master record regions are fluidized. In this manner, a vectorial magneticfield M, provided by the magnetizer 34 is capable of orienting the particles 25 in the particular cyan matrix regions in parallel to the x-axis.

After termination of the exposure step of FIG. 9a, the recording medium 10 is subjected to a degaussing step 63 and is thereupon exposed to a magenta radiation through the master record 100. The requisite magenta radiation is realized with the 103. I I The magenta radiations penetrate the blue and red regions of the master record 100 and the magenta filter elements below these two regions. In consequence, a vectorial magnetic field M, is capable of orienting the particles in the corresponding matrix portions in parallel to the y-axis.

After completion of the exposure step of FIG. 9b, the recording medium 10' is subjected to a degaussing step 63 and is thereupon exposed to yellow light through the master record 100. Theyellow light is provided with the aid of a yellow filter 105.

The yellow light penetrates the red region of the master record 100 and also the yellow filter element below such region. The corresponding yellow matrix region therefore becomes fluidized and a vectorial magnetic field M is capable of orienting the particles in that matrix region inparallel to the z-axis. This exposure step is followed by a degaussing operation 63 and the result is a record in which color components of an image are again expressed in terms of selective particle orientation and disorientation. By way of comparison, it will be recognized that the recording process of FIGS. 6a through 60 proceeded on the basis of a selective disorientation of previously oriented anisotropic particles,

7 while the recording process of FIGS. 9a through 90 proceeds on the basis of a selective orientation of previously disoriented or randomized particles.

The color information record produced by the process of FIGS. .91: through 90' may be printed out in th manner shown in FIGS. la through lltlc.

For this purpose, the recording medium M) is subjected to a magnetization step 68 followed by a degaussing operation 78 which result in an exclusive magnetization of the x-oriented particles in the matrix 24. As indicated by the block 108, a red-colored toner is aid of a magenta filter thereupon applied to the recording medium 10, whereby red toner images 109 and will be formed as shown.

After these toner images have been temporarily fixed in the previously described manner, the recording medium llfi'is subjected to a degaussing step 63, magnetization step 72 and special degaussing step 78 which jointly result in an exclusive magnetization of yoriented particles.

As shown by-the block 112 in FIG. l0b, a greencolored magnetic toner is thereupon applied to the recording medium lit). The result of this toning operation is a formation of green toner images 113 and 114. A temporary fixation of these toner images is followed by a degaussing step 63, a magnetization step 74 and a special degaussing operation 78 which results in an exclusive magnetization of z-oriented particles.

The block H6 in FIG. 10c is symbolic of a toning step with blue-colored magnetic toner that results in the formation of a blue toner image 117. This last toning step is followed by the toner transfer 90 which results in the provision of a color print that contains the transferred toner images. In this print, the toner image I09 provides a red image component that, as desired, corresponds to the red color region of the master record 70 shown in FIG. 6a. The red and green toner images Tilt) and 113 combine to form a yellow print component that corresponds to the yellow color component of the master record 70. The green and blue toner images 1114 and i117 combine to form a cyan print component that corresponds to the cyan color region of the master record 70. As before, white or transparent print regions are-the result of a lack of toner'attraction.

In all the printout processes herein described, the toner particles may be of a fusible type and adjacent dots of different color toner piles may be intermixed during the fusing step. I

It will now be recognized that the subject invention provides very effective color recording methods, apparatus and media, as well asadvanced color records that may repeatedly be subjected to magnetization and printout steps for the production of large numbers of color prints for transparency. The invention also provides a production of positive color prints from positive records and positive color prints from negative records. In general, the production of positive prints from posi tive records or images is preferred in practice.

While specific embodiments have been described and illustrated herein, modifications within the spirit and scope of the subject invention will be apparent or suggest themselves to those skilled in the art.

I claim: 5

ll. In a method of recording at least first and second color components of an image, the improvement comprising in combination the steps of:

providing color component deriving devices for deriving said color components;

providing first and second groups of substantially spherical, magnetizable, uniaxially anisotropic particles in a matrix;

providing said first and second color components with the aid of said color component deriving devices and said image;

selectively orienting and disorienting particles in said first groups to provide a record of saidv provided first color component; and

selectively orienting and disorienting particles in said second groups to provide a record of said provided second color component.

2. A method as claimed in claim 1, including the further steps of:

providing magnetic printout agents;

magnetically printing out said record of said first color component with one of said magnetic printout agents; and magnetically printing out said record of said second color component with anotherof said magnetic printout agents. I

3. A method as claimed in claim 1, wherein:

said particles are single-domain particles.

4. In a method of recording at least first and second color components of an image, the improvement comprising in combination the steps of:

providing color component deriving devices for deriving said color components; providing first and second groups of anisotropic magnetizable particles in a matrix; 1 orienting particles in said first groups substantially in parallel to a first axis; orienting particles in said second groups substantially in parallel to a second axis different from said first axis;

providing said first and second color components with the aid of said color component deriving devices and said image;

changing the orientation of particles in selected groups of said first groups to provide a record of said provided first color component; and

changing the orientation of particles in selected groups of said provided second groups to provide a record of said second color component.

5. A method as claimed in claim 4, wherein:

said particles in said first and second groups areuniaxially anisotropic, single-domain, ferromagnetic particles of a material selected from the group consisting of hexagonal cobalt, manganese bismuthide (MnBi), anda cobalt compound of the type Co,-,R, wherein R is a rare-earth metal. 7

6. A method as claimed in claim 4, wherein:

said particles in said first and second groups are spherical; magnetizable, uniaxially anisotropic ferromagnetic particles.

7. A method as claimed in claim 6, wherein:

said particles are single-domain particles.

8. A method as claimed in claim 4, wherein:

said second axis is made orthogonal tosaid first axis.

9. Amethod as claimed in claim 4, wherein:

said first and second axes are made to extend at like angles to a surface of said matrix.

10.. A method as claimed in claim 4, wherein:

the orientation of particles in said 'selected first groups is changed by disorienting the particles in said selected first groups relative to said first and second axes; and v the orientation of particles in said selected second groups is changed by disorienting the particles in said selected second groups relative to said first and second axes.

ll. Amethod as claimed in claim 4, wherein:

said particles in said first and second groups are spherical, magnetizable, uniaxially anisotropic ferromagnetic particles;

said matrix is made of a material having a first state in which the particles in said first and second groups are substantially stationary, and being transformable into a second state in which said particles are rotationally mobile;

the orientation of particles in said selected first groups is changed by magnetizing the particles in said first groups, and temporarily transforming to said second state selected first portions of said matrix so that particles in said selected first groups will rotate to realize a magnetic low-energy state in said selected first groups; and

the orientation of particles in said selected second groups is changed by magnetizing the particles in said second groups, and temporarily transforming to said second state selected second portions of said matrix so that particles in said selected first groups will rotate to realize a magnetic low-energy state in said selected second groups.

12. A method as claimed in claim 11, wherein:

said particles are single-domain particles.

13. A method as claimed in claim 4, wherein:

said particles in said first and second groups are spherical, magnetizable, uniaxially anisotropic ferromagnetic particles;

said matrix is made of a material having a first state in which the particles in said first and second groups are substantially stationary, and being transfonnable into a second state in which said particles are rotationally mobile;

particles in said first groups are oriented by temporarily transforming first portions of said matrix occupied by said first groups into said second state and magnetically orienting particles in said first matrix portions substantially in parallel to said first axis; and

particles in said second groups are oriented by temporarily transforming second portions of said matrix occupied by said second groups into said second state andmagnetically orienting particles in said second matrix portions substantially in parallel to said second axis.

14. A method as claimed in claim 13, wherein:

said particles are single-domain particles.

15. A method as claimed in claim 13, wherein:

the orientation of particles in said selected first groups is changed by magnetizing the particles in said first groups, and temporarily transforming to said second state selected ones of said first matrix portions whereby particles in said selected first groups will rotate to realize a magnetic low-energy state in said selected first groups; and

the orientation of particles in said selected second groups is changed by magnetizing the particles in said second groups, and temporarily transforming to said second state selected ones of said second matrix portions whereby particles in said selected second groups will rotate to realize a magnetic lowenergy state in said selected second groups.

16. A method as claimed in claim 4, including the steps of:

providing magnetic printout agents;

magnetically printing out said record of said first color component with one of said magnetic printout agents; and

in parallel to a third axis different from said first and second axes; and

the orientation of particles in selected groups of said third groups is changed to provide a record of said provided third color component.

18. In a method of recording at least first and second color components of an image, the improvement comprising in combination the'steps of:

providing color component deriving devices for deriving said color components; I providing first and second groups of anisotropic mag netizable particles in a matrix; providing said first and second color components with the aid of said color component deriving devices and said image; i orienting particles in selected groups of said first groups substantially in parallel to a first axis to provide a record of said provided first color component; and orienting particles in selected groups of said second groups substantially in parallel to a second axis different from said first axis to provide a record of said provided second color component.

19. A method as claimed in claim l8, wherein:

said particles in said first and second groups are uniaxially. anisotropic, single-domain, ferromagnetic particles of a material selected from the group consisting of hexagonal cobalt, manganese bismuthide (MnBi), and a cobalt compound of the type Co R, wherein R is a rare-earth metal.

20. A method as claimed in claim 18, wherein:

said particles in said first and second groups are spherical, magnetizable, uniaxially anisotropic ferromagnetic particles.

21. A method as claimed in claim 20, wherein:

said particles are single-domain particles.

22. A method as claimed in claim 18, wherein:

said second axis is made orthogonal to said first axis.

23. A method as claimed in claim 18, wherein:

said first and second axes are made to extend at like angles to a surface of said matrix.

24. A method as claimed in claim 18, wherein:

said particles in said first and second groups are spherical, magnetizable, uniaxially anisotropic ferromagnetic particles;

said matrix is made of a material having a first state in which the particles in said first and second groups are substantially stationary, and being transformable into a second state in which said particles are rotationally mobile;

particles in said selected first groups are oriented by temporarily transforming first portions of said matrix occupied by said first groups into said second 22 state and magnetically orienting particles in said first matrix portions substantially in parallel to said first axis; and particles in said selected second groups are oriented ,5 by temporarily transforming second portions of said rnatrix occupied by said second groups into said second state and magnetically orienting particles in said second matrix portions substantially in parallel to said second axis.

25. A method as claimed in claim 24, wherein:

said particles are single-domain particles.

.26. A method as claimed in claim 18, including the steps of:

providing magnetic printout agents;

magnetically printing out said record of said first color component with one of said magnetic printout agents; and

magnetically printing out said record of said second color component with another of said magnetic 2O printout agents.

27. A method as claimed'in claim 18, wherein:

said image has a third color component;

further color component driving devices are pro- 25 vided for deriving said third color component;

a third group of anisotropic ferromagnetic particles is provided in said matrix; said third color component is provided with the aid of said further color component deriving devices and said image; and

particles in selected groups of said third groups are oriented substantially in parallel to a third axis different from said first and second axes so as to provide a record of said provided third color component.

28. In a method of printing out a record of at least two color components of an image, in which a first color component is recorded in selectively oriented and disoriented first groups of anisotropic magnetizable particles, and a second color componentis recorded in selectively oriented and disoriented second groups of anisotropic magnetizable particles, the improvement comprising in combination the steps of:

magnetizing only the oriented first groups of particles;

printing out a record of the magnetization of said magnetized first groups with the aid of a first magnetic color toner; magnetizing only the oriented second groups of particles; and

printing out a record of the magnetization of said magnetized second groups with the aid of a second magnetic color toner.

29. A method as claimed in claim 28, including the steps .of: I

subjecting said first and second groups of particles,

after magnetization of the oriented first particle groups and before printout of the magnetized first groups, as well as after magnetization of the oriented second particle groups and before printout of the magnetized second groups, to magnetic demagnetizing fields having a maximum amplitude below a single-particle coercivity of the particles in said first and second groups and above one-half said single-particle coercivity whereby to demagnetize disoriented particles in said first and second groups.

30. In a method of printing out, with a magnetic printout agent, an information record represented by selectively oriented magnetizable anisotropic particles and relatively disoriented magnetizable particles, the improvement comprising in combination the steps of:

subjecting said oriented and said disoriented particles to magnetizing fields; and

subjecting said oriented and said disoriented particles to magnetic demagnetizing fields having a maximum amplitude below a single-particle coercivity of said. oriented and said disoriented particles and above one-half said single-particle coercivity.

31. In apparatus for recording at least first and second color components of an image, the improvement comprising in combination:

first and second color component deriving devices for deriving said first and second color components, respectively;

a recording 'mediumhaving a matrix, and first and second groups of spherical, magnetizable, uniaxially anisotropic particles located in said matrix;

means operatively associated with said first color component deriving devices and said recording medium for providing a record of said first color component by. selectively orienting and disorienting particles in said first groups; and

means operatively associated with said second color component driving devices and said recording medium for providing a record of said second color component by selectively orienting and disorienting particles in said second groups.

32. An apparatus as claimed in claim 31, wherein:

said particles are single-domain particles. p

33. Apparatus as claimed in claim 31, including in said combination:

means oepratively associated with said recording me dium for magnetically printing out said record of the first color component, said first color component printout means include means for providing a ,first magnetic printout agent; and

means operatively associatedzwith said recording medium -forf magnetically printing out said record of the second color component, said second color component printout means include means for providing a second magentic printout agent..

34. In apparatus for recording at least first and second color components of an image, the improvement comprising in combination:

first and second color component deriving devices for deriving said first and second color components, respectively; a recording medium having a matrix, and first and second groups of anisotropic magnetizable particles located in said matrix; means operatively associated with said recording medium for orienting particles in said first groups sub stantially in parallel to a first axis; means operatively associated with said recording medium for orienting particles in said second groups substantially in parallel to a second axis different .from said first axis; means operatively associated with said first color component deriving devices and said recording medium for providing a record of said first color component by changing the orientation of particles in selected groups of said first groups; and

means operatively associated with said second color component deriving devices and said recording medium for providing a record of said second color component by changing the orientation of particles in selected groups of said second groups.

35. Apparatus as claimed in claim 34, wherein:

said means for changing the orientation of particles in selected groups of said first groups include means operatively associated with said first color component deriving devices and said recording medium for providing a record of said first color component by disorienting the particles in said selected first groups relative to said first and second axes; and i said means for changing the orientation of particles in selected groups of said second group include means operatively associated with said second color component deriving devices and said recording medium for providing a record of said second color component by disorienting the particles in said selected second groups relative to said first and second axes.

36. Apparatus as claimed in claim 34, wherein:

said particles in said first and second groups are uniaxially anisotropic, single-domain, ferromagnetic particles of a material selected from the group consisting of hexagonal cobalt, manganese bismuthide (MnBi), and a cobalt compound of the type Co R, wherein R is a rare-earth metal.

37. Apparatus as claimed in claim 34, wherein:

said particles in said first and second groups are spherical, magnetizable, uniaxially anisotropic particles.

38. Apparatus as claimed in claim 37, wherein:

said particles are single-domain particles.

39. In apparatus for recording at least first and second color components of an image, the improvement comprising in combination:

first and second color component deriving devices for deriving saidfirst'and second color components, respectively;

a recording medium hailing a matrix, and first and second groups-of anisotropic magnetizable particles located in said matrix;

means operatively associated with said first color component deriving devices and said recording medium for providing a record of said first color component by orienting particles in selected groups of said firstgroups substantially in parallel to a first axis; and

- means operatively associated with said second color component deriving devices and said recording medium for providing a record of said second color component by orienting particles in selected groups of said second groups in parallel to a second axis different from said first axis.

v40. Apparatus as claimed in claim 39, wherein:

said particles in said first and second groups are uniaxially anisotropic, single-domain, ferromagnetic particles of a material selected from the group consisting of hexagonal cobalt, manganese bismuthide (MnBi), and a cobalt compound of the type Co =,R, wherein R is a rare-earth metal.

41. Apparatus as claimed in claim 39, wherein:

said particles in said first and second groups are spherical, magnetizable, uniaxially anisotropic particles. 

1. In a method of recording at least first and second color components of an image, the improvement comprising in combination the steps of: providing color component deriving devices for deriving said color components; providing first and second groups of substantially spherical, magnetizable, uniaxially anisotropic particles in a matrix; providing said first and second color components with the aid of said color component deriving devices and said image; selectively orienting and disorienting particles in said first groups to provide a record of said provided first color component; and selectively orienting and disorienting particles in said second groups to provide a record of said provided second color component.
 2. A method as claimed in claim 1, including the further steps of: providing magnetic printout agents; magnetically printing out said record of said first color component with one of said magnetic printout agents; and magnetically printing out said record of said second color component with another of said magnetic printout agents.
 3. A method as claimed in claim 1, wherein: said particles are single-domain particles.
 4. In a method of recording at least first and second color components of an image, the improvement comprising in combination the steps of: providing color component deriving devices for deriving said color components; providing first and second groups of anisotrOpic magnetizable particles in a matrix; orienting particles in said first groups substantially in parallel to a first axis; orienting particles in said second groups substantially in parallel to a second axis different from said first axis; providing said first and second color components with the aid of said color component deriving devices and said image; changing the orientation of particles in selected groups of said first groups to provide a record of said provided first color component; and changing the orientation of particles in selected groups of said provided second groups to provide a record of said second color component.
 5. A method as claimed in claim 4, wherein: said particles in said first and second groups are uniaxially anisotropic, single-domain, ferromagnetic particles of a material selected from the group consisting of hexagonal cobalt, manganese bismuthide (MnBi), and a cobalt compound of the type Co5R, wherein R is a rare-earth metal.
 6. A method as claimed in claim 4, wherein: said particles in said first and second groups are spherical, magnetizable, uniaxially anisotropic ferromagnetic particles.
 7. A method as claimed in claim 6, wherein: said particles are single-domain particles.
 8. A method as claimed in claim 4, wherein: said second axis is made orthogonal to said first axis.
 9. A method as claimed in claim 4, wherein: said first and second axes are made to extend at like angles to a surface of said matrix.
 10. A method as claimed in claim 4, wherein: the orientation of particles in said selected first groups is changed by disorienting the particles in said selected first groups relative to said first and second axes; and the orientation of particles in said selected second groups is changed by disorienting the particles in said selected second groups relative to said first and second axes.
 11. A method as claimed in claim 4, wherein: said particles in said first and second groups are spherical, magnetizable, uniaxially anisotropic ferromagnetic particles; said matrix is made of a material having a first state in which the particles in said first and second groups are substantially stationary, and being transformable into a second state in which said particles are rotationally mobile; the orientation of particles in said selected first groups is changed by magnetizing the particles in said first groups, and temporarily transforming to said second state selected first portions of said matrix so that particles in said selected first groups will rotate to realize a magnetic low-energy state in said selected first groups; and the orientation of particles in said selected second groups is changed by magnetizing the particles in said second groups, and temporarily transforming to said second state selected second portions of said matrix so that particles in said selected first groups will rotate to realize a magnetic low-energy state in said selected second groups.
 12. A method as claimed in claim 11, wherein: said particles are single-domain particles.
 13. A method as claimed in claim 4, wherein: said particles in said first and second groups are spherical, magnetizable, uniaxially anisotropic ferromagnetic particles; said matrix is made of a material having a first state in which the particles in said first and second groups are substantially stationary, and being transformable into a second state in which said particles are rotationally mobile; particles in said first groups are oriented by temporarily transforming first portions of said matrix occupied by said first groups into said second state and magnetically orienting particles in said first matrix portions substantially in parallel to said first axis; and particles in said second groups are oriented by temporarily transforming second portions of said matrix occupied by said second groups into said second state and magnetically oriEnting particles in said second matrix portions substantially in parallel to said second axis.
 14. A method as claimed in claim 13, wherein: said particles are single-domain particles.
 15. A method as claimed in claim 13, wherein: the orientation of particles in said selected first groups is changed by magnetizing the particles in said first groups, and temporarily transforming to said second state selected ones of said first matrix portions whereby particles in said selected first groups will rotate to realize a magnetic low-energy state in said selected first groups; and the orientation of particles in said selected second groups is changed by magnetizing the particles in said second groups, and temporarily transforming to said second state selected ones of said second matrix portions whereby particles in said selected second groups will rotate to realize a magnetic low-energy state in said selected second groups.
 16. A method as claimed in claim 4, including the steps of: providing magnetic printout agents; magnetically printing out said record of said first color component with one of said magnetic printout agents; and magnetically printing out said record of said second color component with another of said magnetic printout agents.
 17. A method as claimed in claim 4, wherein: said image has a third color component; further color component deriving devices are provided for deriving said third color component; a third group of anisotropic magnetizable particles is provided in said matrix; said third color component is provided with the aid of said further color component deriving devices and said image; particles in said third group are oriented substantially in parallel to a third axis different from said first and second axes; and the orientation of particles in selected groups of said third groups is changed to provide a record of said provided third color component.
 18. In a method of recording at least first and second color components of an image, the improvement comprising in combination the steps of: providing color component deriving devices for deriving said color components; providing first and second groups of anisotropic magnetizable particles in a matrix; providing said first and second color components with the aid of said color component deriving devices and said image; orienting particles in selected groups of said first groups substantially in parallel to a first axis to provide a record of said provided first color component; and orienting particles in selected groups of said second groups substantially in parallel to a second axis different from said first axis to provide a record of said provided second color component.
 19. A method as claimed in claim 18, wherein: said particles in said first and second groups are uniaxially anisotropic, single-domain, ferromagnetic particles of a material selected from the group consisting of hexagonal cobalt, manganese bismuthide (MnBi), and a cobalt compound of the type Co5R, wherein R is a rare-earth metal.
 20. A method as claimed in claim 18, wherein: said particles in said first and second groups are spherical, magnetizable, uniaxially anisotropic ferromagnetic particles.
 21. A method as claimed in claim 20, wherein: said particles are single-domain particles.
 22. A method as claimed in claim 18, wherein: said second axis is made orthogonal to said first axis.
 23. A method as claimed in claim 18, wherein: said first and second axes are made to extend at like angles to a surface of said matrix.
 24. A method as claimed in claim 18, wherein: said particles in said first and second groups are spherical, magnetizable, uniaxially anisotropic ferromagnetic particles; said matrix is made of a material having a first state in which the particles in said first and second groups are substantially stationary, and being transformable inTo a second state in which said particles are rotationally mobile; particles in said selected first groups are oriented by temporarily transforming first portions of said matrix occupied by said first groups into said second state and magnetically orienting particles in said first matrix portions substantially in parallel to said first axis; and particles in said selected second groups are oriented by temporarily transforming second portions of said matrix occupied by said second groups into said second state and magnetically orienting particles in said second matrix portions substantially in parallel to said second axis.
 25. A method as claimed in claim 24, wherein: said particles are single-domain particles.
 26. A method as claimed in claim 18, including the steps of: providing magnetic printout agents; magnetically printing out said record of said first color component with one of said magnetic printout agents; and magnetically printing out said record of said second color component with another of said magnetic printout agents.
 27. A method as claimed in claim 18, wherein: said image has a third color component; further color component driving devices are provided for deriving said third color component; a third group of anisotropic ferromagnetic particles is provided in said matrix; said third color component is provided with the aid of said further color component deriving devices and said image; and particles in selected groups of said third groups are oriented substantially in parallel to a third axis different from said first and second axes so as to provide a record of said provided third color component.
 28. In a method of printing out a record of at least two color components of an image, in which a first color component is recorded in selectively oriented and disoriented first groups of anisotropic magnetizable particles, and a second color component is recorded in selectively oriented and disoriented second groups of anisotropic magnetizable particles, the improvement comprising in combination the steps of: magnetizing only the oriented first groups of particles; printing out a record of the magnetization of said magnetized first groups with the aid of a first magnetic color toner; magnetizing only the oriented second groups of particles; and printing out a record of the magnetization of said magnetized second groups with the aid of a second magnetic color toner.
 29. A method as claimed in claim 28, including the steps of: subjecting said first and second groups of particles, after magnetization of the oriented first particle groups and before printout of the magnetized first groups, as well as after magnetization of the oriented second particle groups and before printout of the magnetized second groups, to magnetic demagnetizing fields having a maximum amplitude below a single-particle coercivity of the particles in said first and second groups and above one-half said single-particle coercivity whereby to demagnetize disoriented particles in said first and second groups.
 30. In a method of printing out, with a magnetic printout agent, an information record represented by selectively oriented magnetizable anisotropic particles and relatively disoriented magnetizable particles, the improvement comprising in combination the steps of: subjecting said oriented and said disoriented particles to magnetizing fields; and subjecting said oriented and said disoriented particles to magnetic demagnetizing fields having a maximum amplitude below a single-particle coercivity of said oriented and said disoriented particles and above one-half said single-particle coercivity.
 31. In apparatus for recording at least first and second color components of an image, the improvement comprising in combination: first and second color component deriving devices for deriving said first and second color components, respectively; a recording medium hAving a matrix, and first and second groups of spherical, magnetizable, uniaxially anisotropic particles located in said matrix; means operatively associated with said first color component deriving devices and said recording medium for providing a record of said first color component by selectively orienting and disorienting particles in said first groups; and means operatively associated with said second color component driving devices and said recording medium for providing a record of said second color component by selectively orienting and disorienting particles in said second groups.
 32. An apparatus as claimed in claim 31, wherein: said particles are single-domain particles.
 33. Apparatus as claimed in claim 31, including in said combination: means oepratively associated with said recording medium for magnetically printing out said record of the first color component, said first color component printout means include means for providing a first magnetic printout agent; and means operatively associated with said recording medium for magnetically printing out said record of the second color component, said second color component printout means include means for providing a second magentic printout agent.
 34. In apparatus for recording at least first and second color components of an image, the improvement comprising in combination: first and second color component deriving devices for deriving said first and second color components, respectively; a recording medium having a matrix, and first and second groups of anisotropic magnetizable particles located in said matrix; means operatively associated with said recording medium for orienting particles in said first groups substantially in parallel to a first axis; means operatively associated with said recording medium for orienting particles in said second groups substantially in parallel to a second axis different from said first axis; means operatively associated with said first color component deriving devices and said recording medium for providing a record of said first color component by changing the orientation of particles in selected groups of said first groups; and means operatively associated with said second color component deriving devices and said recording medium for providing a record of said second color component by changing the orientation of particles in selected groups of said second groups.
 35. Apparatus as claimed in claim 34, wherein: said means for changing the orientation of particles in selected groups of said first groups include means operatively associated with said first color component deriving devices and said recording medium for providing a record of said first color component by disorienting the particles in said selected first groups relative to said first and second axes; and said means for changing the orientation of particles in selected groups of said second group include means operatively associated with said second color component deriving devices and said recording medium for providing a record of said second color component by disorienting the particles in said selected second groups relative to said first and second axes.
 36. Apparatus as claimed in claim 34, wherein: said particles in said first and second groups are uniaxially anisotropic, single-domain, ferromagnetic particles of a material selected from the group consisting of hexagonal cobalt, manganese bismuthide (MnBi), and a cobalt compound of the type Co5R, wherein R is a rare-earth metal.
 37. Apparatus as claimed in claim 34, wherein: said particles in said first and second groups are spherical, magnetizable, uniaxially anisotropic particles.
 38. Apparatus as claimed in claim 37, wherein: said particles are single-domain particles.
 39. In apparatus for recording at least first and second color components of an image, the improvement comprising in combination: first and second colOr component deriving devices for deriving said first and second color components, respectively; a recording medium having a matrix, and first and second groups of anisotropic magnetizable particles located in said matrix; means operatively associated with said first color component deriving devices and said recording medium for providing a record of said first color component by orienting particles in selected groups of said first groups substantially in parallel to a first axis; and means operatively associated with said second color component deriving devices and said recording medium for providing a record of said second color component by orienting particles in selected groups of said second groups in parallel to a second axis different from said first axis.
 40. Apparatus as claimed in claim 39, wherein: said particles in said first and second groups are uniaxially anisotropic, single-domain, ferromagnetic particles of a material selected from the group consisting of hexagonal cobalt, manganese bismuthide (MnBi), and a cobalt compound of the type Co5R, wherein R is a rare-earth metal.
 41. Apparatus as claimed in claim 39, wherein: said particles in said first and second groups are spherical, magnetizable, uniaxially anisotropic particles.
 42. Apparatus as claimed in claim 41, wherein: said particles are single-domain particles.
 43. In apparatus for printing out a record of at least two color components of an image with the aid of first and second magnetic color toners, in which record selectively oriented and disoriented first groups of anisotropic magnetizable particles represent a first color component, and selectively oriented and disoriented second groups of anisotropic magnetizable particles represent a second color component, the improvement comprising in combination: means operatively associated with said record for magnetizing only the oriented first groups of particles; means operatively associated with said record for printing out a record of the magnetization of said magnetized first groups with said first color toner; means operatively associated with said record for magnetizing only the oriented second groups of particles; and means operatively associated with said record for printing out a record of the magnetization of said magnetized second groups with said second color toner.
 44. Apparatus as claimed in claim 43, including: means operatively associated with said record for subjecting said first and second groups of particles to magnetic demagnetizing fields having a maximum amplitude below a single-particle coercivity of the particles in said first and second groups and above one-half said single-particle coercivity whereby to demagnetize disoriented particles in said first and second groups.
 45. Apparatus for improving the magnetic contrast of an information record represented by selectively magnetized and oriented anisotropic particles, and relatively disoriented magnetized particles, comprising in combination: means operatively associated with said record for subjecting said oriented and said disoriented particles to variable magnetic demagnetizing fields; and means connected to said operatively associated means for adjusting the maximum amplitude of said magnetic demagnetizing fields to a value below a single-particle coercivity of said oriented and said disoriented particles and above one-half of said single-particle coercivity, whereby said disoriented particles are demagnetized and said oriented particles remain magnetized.
 46. A recording medium for recording at least two color components of a luminous image, comprising in combination: means including a plurality of interspersed first filter elements for passing luminous impressions corresponding to one of said color components and second filter elements for passing luminous impressions corresponding to the other of said color components; a matrix; anisotropic magneTizable particles dispersed in said matrix; and means operatively associated with said interspersed first and second filter elements and with said matrix for selectively rotating anisotropic particles in said matrix in response to said passed luminous impressions.
 47. A recording medium as claimed in claim 46, wherein: said anisotropic particles are uniaxially anisotropic, single-domain, ferromagnetic particles of a material selected from the group consisting of hexagonal cobalt, manganese bismuthide (MnBi), and a cobalt compound of the type Co5R, wherein R is a rare-earth metal.
 48. A recording medium as claimed in claim 46, wherein: said particles are spherical, magnetizable, uniaxially anisotropic particles.
 49. A recording medium as claimed in claim 48, wherein: said particles are single-domain particles.
 50. A recording medium as claimed in claim 46, wherein: said matrix has a first state in which said dispersed particles are substantially stationary, and is transformable into a second state in which said particles are rotationally mobile; and said operatively associated means include means for selectively transforming said matrix into said second state in response to said luminous impressions.
 51. A record of at least first and second color components of an image derived by first and second color component deriving devices, respectively, comprising in combination: a matrix; first groups of selectively oriented and relatively disoriented anisotropic magnetizable particles located in said matrix and representing said first color component derived by said first color component deriving devices; and second groups of selectively oriented and relatively disoriented anisotropic magnetizable particles located in said matrix and representing said second color component derived by said second color component deriving devices.
 52. A record as claimed in claim 51, wherein: the oriented particles in said first groups are oriented parallel to a first axis; the oriented particles in said second groups are oriented parallel to a second axis different from said first axis; and the disoriented particles in said first groups and the disoriented particles in said second groups are disoriented relative to said first and second axes.
 53. A record as claimed in claim 51, wherein: said particles in said first and second groups are uniaxially anisotropic, magnetizable, ferromagnetic particles of a material selected from the group consisting of hexagonal cobalt, manganese bismuthide (MnBi), and a cobalt compound of the type Co5R, wherein R is a rare-earth metal.
 54. A record as claimed in claim 53, wherein: said particles are single-domain particles.
 55. A record as claimed in claim 51, wherein: said particles in said first and second groups are spherical, single-domain, uniaxially anisotropic particles.
 56. A record as claimed in claim 51, wherein: said image includes a third color component derived by third color component deriving devices; and said record includes third groups of selectively oriented and relatively disoriented anisotropic magnetizable particles located in said matrix and representing said third color component.
 57. A record as claimed in claim 56, wherein: the oriented particles in said first groups are oriented parallel to a first axis; the oriented particles in said second groups are oriented parallel to a second axis different from said first axis; the oriented particles in said third groups are oriented parallel to a third axis different from said first and second axes; and said disoriented particles in said first, second and third groups are disoriented relative to said first, second and third axes.
 58. A record as claimed in claim 56, wherein: said first, second and third axes extend at like angles to a surface of said matrix. 